1. Field of the Invention
This invention relates to methods for continuously winding transversely perforated plastic film into larger-diameter rolls. It further relates to methods for transferring a moving film from a fully wound roll on a first bare winding shaft onto a second bare shaft. It especially relates to methods for enabling large-diameter rolls of perforated plastic film to be unloaded from a bare shaft.
2. Review of the Prior Art
When winding rolls of a plastic film, several problems occur because of the characteristics of the film. Slipperiness of the film is one such characteristic. If the film is in the form of a narrow strip which is folded lengthwise, sealed lengthwise, and gussetted to form a tube, uneven thickness creates difficulties. If the folded, sealed, and gussetted tube is also transversely perforated and sealed, there are further operational problems.
The reason therefor is that transversely perforated plastic film can withstand very little tensional force without being separated. Consequently, in a turret winding operation on a first bare expandable shaft which is disposed at a winding position, a transversely perforated plastic film cannot be wound with sufficient tension to form a compact and rigid finished roll. This difficulty is magnified when the roll of plastic film is a center-unwindable roll having an inner diameter of at least about 3 inches. Further, when a plastic film is in the form of a transversely perforated and flattened tube for separation by a consumer into freezer bags, produce bags, and the like, the relatively loose winding of such a narrow center-unwindable roll is accentuated so that telescoping of the roll easily occurs when a sidewise force is placed thereon, such as when unloading the roll from a shaft on which it has been wound. A means for preventing such telescoping, such as minimizing the sidewise force required for unloading a roll from a shaft, is needed.
It is also difficult to transfer a moving strip or tube of such transversely perforated film from a wound roll to a new shaft upon which the strip of film or tube of film is to be wound because the lay-on roll cannot be applied to the moving strip or tube with sufficient force to bend the strip or tube into adequate contact with the new shaft. Accordingly, a means for effecting such transfer, without premature breakage of the strip or roll, is additionally needed.
U.S. Pat. No. 3,053,467 describes expansible shafts, arbors, or mandrels of the fluid pressure type on which a tubular core of rolls of paper may be supported for winding and unwinding. This shaft has a multiplicity of radially movable and self retractable gripping buttons which are actuated by an inflatable, cylindrical air bag.
Such an expansible shaft is further described in U.S. Pat. No. 3,863,857, wherein elongate leaf members are attached to the ends of the buttons and are radially expanded by inflation of the air bladder. These expansible air shafts are primarily intended for gripping a core of a roll of paper or other web material. After winding is completed, the buttons or leaf members are retracted so that the core can be slid endwise from the winding shaft. If individual rolls are to be wound, such as when winding tubes of transversely perforated film to form rolls that can be separated into plastic bags by a consumer, the core may be furnished with a circumferentially attached strip of expansible adhesive tape in order to facilitate transfer of a continuously moving tube onto a new core.
U.S. Pat. No. 2,779,547 describes a winding mandrel with a suction means, comprising a drum mounted for rotation about the axis of a hollow shaft and provided with a slot which is parallel to the axis of rotation of the shaft and runs substantially the length of the drum and in which is positioned a suction box connected at its center to an external vacuum pump through a rotary seal at an end of the mandrel. An aperture pad of non-porous rubber fits into the suction box and has spaced holes along the length thereof to form suction passages. In operation, a moving paper web is drawn by suction at the holes into frictional anchorage upon the pad.
U.S. Pat. No. 3,552,670 describes a web-winding apparatus of the automatic or continuous type for automatically moving a new "core-carrying" mandrel into the path of the web while it is still being wound on a preceding core-carrying mandrel to complete the winding of that roll. The web is fed in partial wrapping engagement over a bed roll to a core on one of a plurality of rotatably mounted winding mandrels carried in revolution by a rotatable turret past a pickup position where the free leading edge of a web formed by transverse severance of the web is transferred to a core disposed in a successive winding mandrel. A stationary vacuum chamber is formed within the interior of the bed roll and communicates through one end to a source of partial vacuum and peripherally through a plurality of holes in the shell of the bed roll. Where light, relatively impervious web materials are involved, such as sanitary tissues having transverse lines of weakness, the shell has relatively few openings through which a partial vacuum acts on the web. The bed roll has openings in the form of slots having a width of about 0.040 inch and a very short radial distance through which the vacuum must act, so that when a breakage occurs at a line of transverse perforations, the loose end of the web is caught very quickly onto the bed roll.
U.S. Pat. No. 3,743,199 describes a vacuum reel spool for use on a paper machine reel when transferring a very light web to a new reel spool. The reel spool comprises a cylindrical shell having a longitudinal axis of rotation and a plurality of perforations which are formed uniformly on the surface of the shell along substantially the entire face width thereof. The interior of the reel spool is connected to a vacuum source, such as a vacuum pump. During operation, the vacuum produced within the reel spool urges the ballooned portion of the web, that is formed between a previously wound roll and a new reel spool, into the nip between the reel drum and the reel spool so that even especially light webs, such as tissue paper, can be reeled continuously when traveling at speeds as high as 3500 feet per minute.
U.S. Pat. No. 4,030,681 describes a winder for plastic film in the absence of a winding core. The winder features equalized air lubrication of the wound roll throughout its axial removal from the arbor. It is particularly directed to rolls of web having small central holes which are less susceptible to crushing.
U.S. Pat. No. 4,327,877 describes a continuous winding device for webs of paper, such as toilet paper, comprising a pair of drums drivable at an equal peripheral speed, the first drum having annular seats with perforated zones for suction orifices adapted to exert a suction during the removal of a finished roll and the insertion of a new core. The suction brings the material into the zone in which the tearing is to take place and inserts the material between the drum and the new inserted core.